Immunoglobulin E (IgE)-mediated insect sting allergy to Hymenoptera is of common occurrence. Hymenoptera stings are classified into normal local reactions, large local reactions, systemic anaphylactic reactions, systemic toxic reactions, and unusual reactions. The most frequent clinical patterns are large local and systemic anaphylactic reactions. Based on the results of four studies, the prevalence of large local sting reactions ranges from 2.4% and 26.4% (for a review, see Biló et al 2005). In children the prevalence yielded by one study is 19%. Nine epidemiologic studies report a prevalence of self-reported systemic anaphylactic sting reactions between 0.3% and 7.5% (for a review, see Biló et al 2005). For most venom-allergic patients an anaphylactic reaction after a sting is a very traumatic event resulting in an altered health-related quality of life. In some instances the anaphylactic reaction may cause death, and this fatal outcome can occur as the first manifestation after a sting (Barnard 1973). Risk factors influencing the outcome of an anaphylactic reaction include the time interval between stings, the number of stings, the severity of the preceding reaction, age, cardiovascular diseases and drug intake, insect type, elevated serum tryptase, and mastocytosis.
Hymenoptera include the family Apidae consisting of the genera Apis (including the species Apis mellifera, honeybee) and Bombus (bumblebees), and the family Vespidae (vespids) consisting of the Vespinae and Polistinae subfamilies. The Vespinae subfamily includes the three genera Vespula (called wasps in Europe, yellow jackets in the USA), Dolichovespula (called hornets in the USA) and Vespa (called hornets in Europe and the USA). In the USA there are many species of Vespula, Dolichovespula and Polistes (called paper wasps in Europe and the USA) (King 1994). Vespine wasps are generally considered to be the most common source of stings, due to their abundance, aggressiveness and relatively large colony size (up to several thousand workers) of some species. In areas with mild winters, including Florida, California and Hawaii multiple queens may inhabit the same nest and produce enormous perennial colonies with a high potential for mass stinging (Greene and Breitsch 2005). Polistine wasps have small colonies of usually no more than a few dozen workers, but their nests can be extremely abundant around human habitations. The most pestiferous species is the recently arrived Polistis dominulus, an invasive European wasp (Greene and Breitsch 2005). Although honeybees are often invoked as a sting hazard, accidental disturbance of feral colonies in the US was rare until recently, because nests were typically located within tree cavities or structural voids. The arrival of Africanized bees (Apis mellifera scutellata) in 1990 markedly increased the stinging risk in several southwestern states, as this subspecies has an extremely low defensive response threshold and is capable of some of the most severe attacks known for any social insect (Greene and Breitsch 2005).
In Europe Vespula species V. vulgaris and V. germanica are dominating. In the genus Dolichovespula the most common species in Europe are D. media, D. saxonia and D. sylvestris and in the genus Vespa, Vespa crabro (European hornet) is the most prevalent in Europe. Among Polistinae (called paper wasps in Europe and the USA), Polistes gallicus, P. nimpha and P. dominulus are widespread especially in the Mediterranean area. In central and northern Europe vespid (mainly Vespula spp.) and honeybee stings are the most prevalent, whereas in the Mediterranean area stings from Polistes and Vespula are more frequent than honeybee stings, bumblebee stings are rare throughout Europe and more of an occupational hazard (Biló et al 2005).
The symptoms of IgE-mediated (type I) sting allergic reactions are due to release of mediators (e.g. histamine) resulting from cross-linking of effector cell-bound IgE antibodies by venom allergens. The symptoms can be suppressed by various pharmacologic treatments, but allergen-specific immunotherapy (SIT) represents the only curative approach. A rise in allergen-blocking IgG antibodies, particularly of the IgG4 class (Wetterwald et al 1985), a reduction in the number of mast cells and eosinophils, and a decreased release of mediators (Varney et al 1993) were found to be associated with successful SIT. Based on these observations, determination of the serum levels of allergen-specific IgE and IgG4 antibodies is useful to describe the immune status of an allergic patient.
In vitro measurement of specific serum IgE antibodies can be performed by the radio-allergosorbent test (RAST), various enzyme-linked immunosorbent assays (ELISA) and other IgE-binding techniques such as immunoelectrophoresis, immunoblot, immunodotblotting, bead array technology and various fluid phase systems. The analytes can also be allergen-specific antibodies of the IgG4 or other IgG subclasses. As an alternative to the above listed assay systems, basophil cells derived from patients or from basophil cell lines such as the KU812 have been used for the in vitro measurement of allergen-specific IgE antibodies in serum by in vitro mediator release assays (MRA). Furthermore, in vivo tests for diagnosis of hymenoptera venom allergy are performed by skin prick or intradermal testing. Such tests are well known in the art (Biló et al 2005).